21n^2-66n-72=0

Solution for 21n^2-66n-72=0 equation:

Simplifying
21n2 + -66n + -72 = 0

Reorder the terms:
-72 + -66n + 21n2 = 0

Solving
-72 + -66n + 21n2 = 0

Solving for variable 'n'.

Factor out the Greatest Common Factor (GCF), '3'.
3(-24 + -22n + 7n2) = 0

Factor a trinomial.
3((-6 + -7n)(4 + -1n)) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(-6 + -7n)' equal to zero and attempt to solve:

Simplifying
-6 + -7n = 0

Solving
-6 + -7n = 0

Move all terms containing n to the left, all other terms to the right.

Add '6' to each side of the equation.
-6 + 6 + -7n = 0 + 6

Combine like terms: -6 + 6 = 0
0 + -7n = 0 + 6
-7n = 0 + 6

Combine like terms: 0 + 6 = 6
-7n = 6

Divide each side by '-7'.
n = -0.8571428571

Simplifying
n = -0.8571428571
Subproblem 2
Set the factor '(4 + -1n)' equal to zero and attempt to solve:

Simplifying
4 + -1n = 0

Solving
4 + -1n = 0

Move all terms containing n to the left, all other terms to the right.

Add '-4' to each side of the equation.
4 + -4 + -1n = 0 + -4

Combine like terms: 4 + -4 = 0
0 + -1n = 0 + -4
-1n = 0 + -4

Combine like terms: 0 + -4 = -4
-1n = -4

Divide each side by '-1'.
n = 4

Simplifying
n = 4
Solution
n = {-0.8571428571, 4}